Model inter-comparison on transport and chemistry : report on model inter-comparison performed within European Commission FP5 project Evergreen ("Global satellite observation of greenhouse gas emissions")

A comprehensive inter-comparison of 5 atmospheric chemistry transport models (TM5, TM4, TM3, IMAGES, and LMDZ) has been performed. The main objective was to analyze differences in model transport, in particular vertical mixing (boundary layer and convective transport), synoptic variations, and large scale global circulation (including inter-hemispheric exchange and stratospheric tropospheric exchange (STE)). For this purpose simulations of various tracers with very different atmospheric lifetimes τ have been carried out: 222Rn (τ = 3.8 days), SF6 (τ = ~3000 years), and CH4 (τ = ~9 years), using prescribed boundary conditions for all models. Furthermore, OH fields from various model simulations with full chemistry have been compared.